U.S. patent application number 14/832477 was filed with the patent office on 2016-02-25 for photovoltaic energy sources.
The applicant listed for this patent is Spinlectrix, Inc.. Invention is credited to Jonathan Forrest Garber, Frank H. Levinson, John Michael Pinneo, Gerald Sage.
Application Number | 20160056759 14/832477 |
Document ID | / |
Family ID | 55349155 |
Filed Date | 2016-02-25 |
United States Patent
Application |
20160056759 |
Kind Code |
A1 |
Pinneo; John Michael ; et
al. |
February 25, 2016 |
PHOTOVOLTAIC ENERGY SOURCES
Abstract
A photovoltaic (PV) panel includes a PV output, a storage and
retrieval subsystem (storage subsystem), and PV cells. The PV
output is configured to be coupled to a distribution system to
supply electricity produced by the PV panel to the distribution
system. The storage subsystem includes a dedicated storage device.
The storage subsystem is electrically coupled to the PV output and
provides per-panel energy storage. The PV cells are coupled to the
PV output and to the storage device. The PV cells are configured to
photovoltaically generate an electrical potential when exposed to
incident illumination. While incident illumination is available,
the PV cells supply a portion of the electrical potential to the PV
output and a second portion to the dedicated energy storage device.
The storage subsystem is configured to intermediately supply energy
stored thereon to the PV output while the incident illumination is
unavailable or partially unavailable.
Inventors: |
Pinneo; John Michael;
(Portola Valley, CA) ; Garber; Jonathan Forrest;
(Hillsborough, CA) ; Levinson; Frank H.; (Tiburon,
CA) ; Sage; Gerald; (Chico, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Spinlectrix, Inc. |
Burlingame |
CA |
US |
|
|
Family ID: |
55349155 |
Appl. No.: |
14/832477 |
Filed: |
August 21, 2015 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
62040180 |
Aug 21, 2014 |
|
|
|
Current U.S.
Class: |
307/23 |
Current CPC
Class: |
H02S 40/32 20141201;
H02S 40/38 20141201; H02S 40/34 20141201; H02S 30/10 20141201; H02S
50/00 20130101 |
International
Class: |
H02S 40/38 20060101
H02S040/38; H02J 5/00 20060101 H02J005/00; H02S 40/34 20060101
H02S040/34; G01R 31/40 20060101 G01R031/40; H02S 30/10 20060101
H02S030/10; H02S 40/32 20060101 H02S040/32 |
Claims
1. A solar photovoltaic (PV) panel configured as a modular
electrical source, the PV panel comprising: an electrical PV output
that is configured to be electrically coupled to a distribution
system such that electricity produced by the PV panel is supplied
to the distribution system; a storage and retrieval subsystem that
includes a dedicated energy storage device, wherein the storage and
retrieval subsystem is electrically coupled to the PV output and
configured to provide per-panel energy storage to the PV panel; and
one or more PV cells that are electrically coupled to the PV output
and electrically coupled to the dedicated energy storage device,
wherein the PV cells are configured to photovoltaically generate an
electrical potential in response to exposure to incident
illumination, and during periods in which incident illumination is
available to the PV cells, to supply a first portion of the
electrical potential to the PV output and a second portion of the
electrical potential to the dedicated energy storage device,
wherein the storage and retrieval subsystem is further configured
to intermediately supply energy stored thereon to the PV output
during periods in which incident illumination is unavailable or
partially unavailable to the PV cells.
2. The PV panel of claim 1, wherein the dedicated energy storage
device is configured such that energy supplied to the PV output by
the dedicated energy storage device maintains a nominal electrical
output of the PV panel for a particular period of time following an
onset of unavailability or partial unavailability of the incident
illumination.
3. The PV panel of claim 2, wherein the particular period of time
is about 10 minutes following the onset of the unavailability or
partial unavailability.
4. The PV panel of claim 2, wherein the nominal electrical output
includes: an unregulated direct current (DC) voltage and DC
current, regulated counterparts of the unregulated DC voltage and
DC current, an alternating current (AC) of a particular voltage, a
particular frequency, and a particular reactive power content, or
an AC of a controllable voltage, a controllable frequency, and a
controllable reactive power content.
5. The PV panel of claim 1, wherein the incident illumination is
unavailable or partially unavailable to the photovoltaic cells when
the electrical output of the panel is decreased by more than about
10% of a nominal electrical output.
6. The PV panel of claim 1, further comprising a frame, wherein the
storage and retrieval subsystem is mechanically attached to the
frame or the storage and retrieval subsystem is physically
incorporated within the frame.
7. The PV panel of claim 1, wherein the storage and retrieval
subsystem includes a bi-directional inverter that is configured to
receive electrical energy from the distribution system during
periods in which energy production in the distribution system
exceeds a load in the distribution system and to store the received
electrical energy in the dedicated energy storage device.
8. The PV panel of claim 1, wherein the dedicated energy storage
device includes one or more or a combination of a flywheel
assembly, an electrochemical storage device, and a pneumatic
storage system.
9. A multi-panel generation system comprising one or more of the PV
panels of claim 1.
10. The PV panel of claim 1, wherein the dedicated energy storage
device is configured such that energy supplied to the PV output by
the dedicated energy storage device exceeds a nominal electrical
output of the PV panel.
11. A storage and retrieval subsystem of a solar photovoltaic (PV)
panel, the storage and retrieval subsystem comprising: a dedicated
energy storage device that is electrically coupled to a PV output
of the PV panel and to a PV device string that produces electricity
in response to exposure to insolation, wherein: the dedicated
energy storage device is configured to receive and store a portion
of the electricity produced by the PV device string and to
intermediately supply the stored energy to the PV output in
response to an indication that the insolation is unavailable or
partially unavailable, and the dedicated energy storage device
provides per-panel energy storage to the PV panel.
12. The storage and retrieval subsystem of claim 11, further
comprising an inverter that is electrically coupled to the
dedicated energy storage device, wherein the inverter is configured
to draw energy from the dedicated energy storage device and convert
the energy from a direct current (DC) electrical potential to an
alternating current (AC) electrical output and supply the AC
electrical output to the PV output.
13. The storage and retrieval subsystem of claim 12, further
comprising a controller that is electrically coupled to the
inverter, wherein the controller is configured to control the
inverter according to a programmed allocation of energy between the
dedicated energy storage device and the PV output and according to
a defined PV panel behavior.
14. The storage and retrieval subsystem of claim 13, further
comprising: a maximum power point transfer (MPPT) device
electrically coupled between the controller and the PV device
string, the MPPT device configured to determine an optimal
current-voltage (IV) point based on environmental conditions of the
PV panel; and a communication unit that is electrically coupled to
the controller and configured to communicate status information of
the dedicated energy storage device.
15. The storage and retrieval subsystem of claim 11, further
comprising battery management electronics that include an isolation
diode, wherein: the dedicated energy storage device includes an
electrochemical storage device, and the electrochemical storage
device supplies energy to the PV output in response to electrical
output at the PV output dropping below a voltage of the
electrochemical storage device.
16. The storage and retrieval subsystem of claim 11, wherein the
dedicated energy storage device includes a flywheel assembly.
17. The storage and retrieval subsystem of claim 16, wherein the
flywheel assembly includes an active magnetic rotor position
control.
18. A solar photovoltaic (PV) panel configured as a modular
electrical source, the PV panel comprising: an electrical PV output
that is configured to be electrically coupled to a distribution
system such that electricity is transferable between the PV panel
and distribution system; a storage and retrieval subsystem that is
electrically coupled to the PV output and configured to provide
per-panel energy storage and to intermediately supply energy stored
thereon to the PV output; and a PV device string that is
electrically coupled to the PV output and to a storage and
retrieval subsystem, wherein: during periods in which insolation is
available to the PV device string an electrical potential is
photovoltaically produced, a first portion of which is supplied to
the PV output and a second portion of the electrical potential is
supplied to the storage and retrieval subsystem, and during periods
in which energy production in the distribution system exceeds a
load in the distribution system, a portion of energy produced in
the distribution system is stored in the dedicated energy storage
device.
19. The PV panel of claim 18, wherein: during periods in which
insolation is unavailable or partially unavailable, some portion of
energy stored on the storage and retrieval subsystem is supplied to
the PV output.
20. The PV panel of claim 18, wherein the storage and retrieval
subsystem includes: a flywheel assembly having active magnetic
rotor position control; a bi-directional inverter that is
electrically coupled to the flywheel assembly, wherein the
bi-directional inverter is configured to draw energy from the
flywheel assembly and supply an electrical output to the PV output
and to receive electrical energy from the distribution system and
supply the electrical energy to the flywheel assembly; a controller
that is electrically coupled to the bi-directional inverter,
wherein the controller is configured to control the bi-directional
inverter according to a programmed allocation of energy between the
flywheel assembly and the PV output and according to a defined PV
panel behavior; a maximum power point transfer (MPPT) device that
is electrically coupled between the controller and the PV device
string, the MPPT device configured to determine an optimal
current-voltage (IV) point based on environmental conditions of the
PV panel; and a communication unit that is electrically coupled to
the controller and configured to communicate status information of
the flywheel assembly.
21. The PV panel of claim 20, wherein the flywheel assembly
includes: an enclosure that is evacuated; a flywheel rotor
positioned within the enclosure; and levitator control electronics
that are configured to re-position the flywheel rotor within the
enclosure in response to the flywheel rotor exiting a spatial
envelope defined in the enclosure.
22. The PV panel of claim 21, wherein the flywheel assembly is
configured to store about 100 Watt-hours of kinetic energy.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of and priority to U.S.
Provisional Application No. 62/040,180 filed Aug. 21, 2014, which
is incorporated herein by reference in its entirety.
FIELD
[0002] Embodiments described herein relate to photovoltaic energy
sources.
BACKGROUND
[0003] Electrical output of a photovoltaic (PV) panel may vary due
to transient obstructions, such as clouds and dust storms. The
obstructions are temporarily positioned between the sun and the PV
panel, which may reduce electrical generation and accordingly
electrical output of the PV panel. Alternatively, obstructions may
include a characteristic that increases the electrical output. For
instance, bright white clouds may reflect some radiation in
addition to that illumination provided by the sun, which may
increase the electrical output. The obstructions may be difficult
to predict and may result in inconsistent and unreliable electrical
output from the PV panel. The inconsistency of the electrical
output contributes to an inability of an electrical grid to
sufficiently rely on the PV panel.
[0004] In general, electrical grids can accommodate some
inconsistency in electrical generation and variations in electrical
loading. This inconsistency in electrical generation and these
variations in electrical loading are usually slow and can be
predictable. For example, a very hot day may be predicted. The very
hot day may have associated with it a high electrical load, which
can be accommodated for in energy markets. Similarly, a particular
utility plant may have a scheduled maintenance period, which may
result in lowered energy supply. Again, the scheduled maintenance
period can be accommodated for in energy markets. For example, the
scheduled maintenance and/or the high electrical load may be
accommodated for by bringing another plant online, operating at a
higher production rate, or purchasing electricity from another
source. However, the output of the PV panel, because of transient
obstructions, may vary quickly and unpredictably. Thus, the
electrical grid cannot accommodate for such output variations of PV
panels.
[0005] The subject matter claimed herein is not limited to
embodiments that solve any disadvantages or that operate only in
environments such as those described above. Rather, this background
is only provided to illustrate one example technology area where
some embodiments described herein may be practiced.
SUMMARY
[0006] An example embodiment includes a solar photovoltaic (PV)
panel. The PV panel may be configured as a modular electrical
source. The PV panel may include an electrical PV output, a storage
and retrieval subsystem, and one or more PV cells. The electrical
PV output is configured to be electrically coupled to a
distribution system such that electricity produced by the PV panel
is supplied to the distribution system. The storage and retrieval
subsystem includes a dedicated energy storage device. The storage
and retrieval subsystem is electrically coupled to the PV output
and configured to provide per-panel energy storage to the PV panel.
The PV cells are electrically coupled to the PV output and
electrically coupled to the dedicated energy storage device. The PV
cells are configured to photovoltaically generate an electrical
potential in response to exposure to incident illumination. During
periods in which incident illumination is available to the PV
cells, the PV cells supply a first portion of the electrical
potential to the PV output and a second portion of the electrical
potential to the dedicated energy storage device. The storage and
retrieval subsystem is configured to intermediately supply energy
stored thereon to the PV output during periods in which incident
illumination is partially unavailable or unavailable to the PV
cells.
[0007] The object and advantages of the embodiments will be
realized and achieved at least by the elements, features, and
combinations particularly pointed out in the claims.
[0008] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory and are not restrictive of the invention, as
claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Example embodiments will be described and explained with
additional specificity and detail through the use of the
accompanying drawings in which:
[0010] FIG. 1A is a block diagram of a photovoltaic (PV) panel;
[0011] FIG. 1B is a block diagram of the PV panel of FIG. 1A
subject to an example transient obstruction;
[0012] FIG. 2 is an example plot depicting output of the PV panel
of FIGS. 1A and 1B;
[0013] FIG. 3 is a plot depicting an example irradiance of an
example PV panel during an example day;
[0014] FIG. 4A is a block diagram of an example PV panel;
[0015] FIG. 4B is a block diagram of the PV panel of FIG. 4A
subject to an example transient obstruction;
[0016] FIG. 5 is an example plot depicting output of the PV panel
of FIGS. 4A and 4B;
[0017] FIG. 6 illustrates an example PV assembly that includes an
embodiment of the PV panel of FIGS. 4A and 4B;
[0018] FIG. 7 illustrates an example embodiment of a storage
subsystem that may be implemented in the PV panel of FIGS. 4A and
4B;
[0019] FIG. 8 illustrates another example embodiment of a storage
subsystem that may be implemented in the PV panel of FIGS. 4A and
4B;
[0020] FIG. 9 illustrates an example embodiment of a storage device
that may be implemented in the PV panel of FIGS. 4A and 4B;
[0021] FIG. 10 illustrates another example embodiment of a storage
device that may be implemented in the PV panel of FIGS. 4A and
4B;
[0022] FIG. 11A illustrates another example embodiment of a storage
device that may be implemented in the PV panel of FIGS. 4A and
4B;
[0023] FIG. 11B illustrates another view of the storage device of
FIG. 11A;
[0024] FIG. 11C illustrates another view of the storage device of
FIGS. 11A and 11B; and
[0025] FIG. 12 illustrates a levitator assembly that may be
implemented the storage device of FIGS. 11A and 11B,
[0026] all according to at least one embodiment described
herein.
DETAILED DESCRIPTION OF SOME EMBODIMENTS
[0027] FIGS. 1A and 1B illustrate a solar photovoltaic (PV) panel
100. The PV panel 100 includes an interconnected PV device string
102 that includes multiple individual PV cells 104 that are
electrically connected to a PV panel electrical output (PV output)
106. The PV cells 104 are configured to photovoltaically generate
an electric potential in response to exposure to incident
illumination. The incident illumination can be a result of
insolation, which is represented in FIGS. 1A and 1B by an arrow and
labeled 108. The PV output 106 may be electrically coupled to an
electrical distribution system 120. Electricity produced by the PV
panel 100 is supplied to the electrical distribution system 120.
For instance, the PV panel 100 may be incorporated in a residential
electrical distribution system such as a home, which may be an
example of the distribution system 120. Additionally, the PV panel
100 may be incorporated in a public grid, which may be another
example of the distribution system 120. The PV panel 100 of FIGS.
1A and 1B does not include or incorporate a dedicated energy
storage device.
[0028] The PV panel 100 of FIG. 1A is subject to the insolation 108
without a transient obstruction. The insolation 108 without the
transient obstruction is referred to as nominal insolation.
Exposure of the PV panel 100 to the nominal insolation 108 of FIG.
1A results in delivery of a nominal electrical output at the PV
output 106. In general, the nominal electrical output is delivered
to the PV output 106 while nominal insolation 108 is available to
the PV panel 100. In some embodiments, the nominal electrical
output of the PV panel 100 includes an unregulated direct current
(DC) voltage and DC current, regulated counterparts of the
unregulated DC voltage and DC current, or an alternating current
(AC) of a particular voltage, a particular frequency, and
particular reactive power content. The nominal electrical output or
some characteristic thereof may be controllable. For instance, the
particular voltage, the particular frequency, the particular
reactive power content, or some combination thereof may be
controllable. Additionally or alternatively, in some embodiments,
the nominal electrical output or some characteristic thereof may be
predefined.
[0029] FIG. 1B illustrates the PV panel 100 subjected to insolation
108 that is obscured by a transient obstruction 110 represented by
a cloud. The transient obstruction 110 is positioned between the PV
panel 100 or a portion thereof and the insolation 108. The
transient obstruction 110 interrupts availability of the insolation
108 or at least reduces availability of the insolation 108.
Interruption in the insolation 108 results in a reduction in the
electrical output delivered to the PV output 106. FIG. 1B depicts
the transient obstruction 110 as a cloud. However, the insolation
108 may be obscured by multiple types of transient obstructions
110. Some other examples of transient obstructions 110 may include
water, rain, snow, dust, shadows from airplanes or wind turbines,
dust storms, plants or portions thereof (e.g., leaves falling on
the PV panel 100), animals (e.g., swarms of insects), other
environmental conditions, and the like.
[0030] In general, the electrical output of the PV panel 100 is
reduced for a period of time while the transient obstruction 110 is
positioned between the insolation 108 and the PV panel 100 or a
portion thereof. FIG. 2 illustrates a plot 200 that depicts an
example variation in electrical output of the PV panel 100 because
of the transient obstruction 110.
[0031] In the plot 200 of FIG. 2, insolation energy flux per unit
area is plotted along a vertical axis 202. Time is plotted along
the horizontal axis 204 of the plot 200. The insolation energy flux
per unit area, which may be in W/m.sup.2 and electrical output of
the PV panel 100 are linearly related. Accordingly, the vertical
axis 202 serves to illustrate the relationship between both the
electrical output and the insolation energy flux per unit area
during the depicted events. Additionally, the plot 200 includes an
insolation line 206 and an electrical output line 208. With
combined reference to FIGS. 1A-2, the insolation line 206
represents the insolation 108 to which the PV panel 100 is exposed.
The electrical output line 208 represents the electrical output of
the PV panel 100. The plot 200 includes a first period 212 and a
second period 214. The first period 212 is during availability of
the insolation 108 and the second period 214 is during
unavailability or partial unavailability of the insolation 108.
[0032] The first period 212 exists from a time equal to 0 on the
plot 200 to a first time 210 and from a second time 213 onward.
During the first period 212 the electrical output of the PV panel
100 may be the nominal designed electrical output of the PV panel
100. At the first time 210, the transient obstruction 110 begins to
obscure the insolation 108. The transient obstruction 110 may make
the insolation 108 unavailable or partially unavailable. The second
period 214 may include times from the first time 210 to a second
time 213. The second time 213 corresponds to a time at which the
transient obstruction 110 is no longer positioned between the
insolation 108 and the PV panel 100. During the second period 214,
the insolation line 206 and the electrical output line 208 begin to
drop, representing a reduction from nominal insolation 108 and a
corresponding reduction in electrical output of the PV panel 100.
The electrical output and the nominal insolation 108 of the PV
panel 100 may continue to be reduced during the second period 214.
During the second period 214, the transient obstruction 110 may
begin to move away from the PV panel 100, which may increase the
insolation 108 and electrical output of the PV panel 100.
[0033] At the second time 213, the transient obstruction 110 is no
longer positioned between the PV panel 100 and the insolation 108.
Accordingly, the insolation 108 may increase and the electrical
output of the PV panel 100 may also increase. The first period 212
may last from the second time 213 until another transient
obstruction 110 is positioned between the PV panel 100 and the
insolation 108.
[0034] The plot 200 of FIG. 2 represents an example of changes to
the electrical output and the insolation 108 because of a single,
transient obstruction 110. FIG. 3 illustrates a plot 300 that
represents an electrical output of a PV panel (e.g., the PV panel
100) over the course of a day. In FIG. 3, irradiance, also referred
to as insolation in Watts per unit area as well as normalized
electrical output of a PV panel is plotted along a vertical axis
306. Time is plotted along the horizontal axis 310. The plot 300
includes an electrical output line 308 with multiple transient
insolation reductions 302. In the plot 300, the electrical output
represented by the electrical output line 308 has been normalized
to the same scale as an irradiance trace. Because the irradiance
trace and the electrical output co-vary, the electrical output line
308 also represents the irradiance trace and appears as a single
line (e.g., 308).
[0035] From FIG. 3, it can be seen that each of the transient
insolation reductions 302 may last for a brief period of time
(e.g., about five-fifteen minutes). Accordingly, the electrical
output of the PV panel may fluctuate significantly (e.g., up to
100%) in a short period of time (e.g., about thirty seconds) and
remain at this reduced output for a brief period of time. These
fluctuations occur multiple times during the course of the day. In
general, this fluctuation of electrical output introduces
instability into systems (e.g., a power grid) incorporating the PV
panel.
[0036] Accordingly, some embodiments described in this disclosure
include a solar PV panel that is configured as a modular electrical
source. The PV panel includes a PV output, a dedicated energy
storage device, and one or more PV cells. The PV output is
configured to be electrically coupled to an electrical distribution
system and to supply electricity to the electrical distribution
system. The dedicated energy storage device is electrically coupled
to the PV output. The PV cells are electrically coupled to the PV
output and electrically coupled to the dedicated energy storage
device. The PV cells are configured to photovoltaically generate an
electric potential in response to exposure to incident illumination
during periods in which incident illumination is available to the
photovoltaic cells and to supply a first portion of the electrical
potential to the electrical output and a second portion of the
electrical potential to the dedicated energy storage device. The
dedicated energy storage device is configured to intermediately
supply energy stored thereon to the PV output during periods in
which incident illumination is unavailable or partially unavailable
to the PV cells.
[0037] In some embodiments, the dedicated energy storage device
includes a flywheel assembly. The flywheel assembly may further
include rolling element bearings, passive magnetic bearings, an
active magnetic rotor with position control, or some combination
thereof. In some embodiments, the dedicated energy storage device
may include an electrochemical storage device (e.g., a battery) or
a pneumatic storage system. Additionally, in some embodiments, the
dedicated energy storage device may include some combination of the
flywheel, the electrochemical battery, and the pneumatic storage
system.
[0038] Although FIGS. 2 and 3 depict reductions in the electrical
output, in some circumstances, presence of the transient
obstruction 110 may increase the electrical output of the PV panel
above a nominal electrical output. The dedicated energy storage
device of the PV panel may be configured to store the excess
electrical output of the PV panel. For example, nominal electrical
output of the PV panel may include about 111 Watts, about 69.4
Volts, and about 1.6 Amperes. Under conditions of the transient
obstruction 110, the electrical output of the PV panel may increase
to about 124 Watts, about 73 Volts, and about 1.7 Amperes. The
dedicated energy storage device may be configured to store the
additional 13 Watts, 3.6 Volts, and 0.1 Amperes, for the duration
of the transient increase.
[0039] In addition, the energy storage device may be configured to
store energy from the distribution system. Thus, the energy storage
device may provide load-following to the distribution system, which
may increase stability of the distribution system.
[0040] Some additional details of this and other embodiments are
discussed with reference to the appended figures. In the appended
figures, like numbers correspond to like structures unless
described otherwise.
[0041] FIGS. 4A and 4B illustrate a solar PV panel 400. The PV
panel 400 is similar to the PV panel 100. The PV panel 400 combines
a storage and retrieval subsystem (storage subsystem) 410 with PV
energy production components (e.g., the interconnected PV device
string 102 and the PV cells 104). The storage subsystem 410 is
configured to mitigate or eliminate electrical output instability
of the PV panel 400. For example, the storage subsystem 410 is
configured as dedicated energy storage of the PV panel 400.
[0042] The PV panel 400 thus stores a portion of the energy
produced while the insolation 108 is available. In addition, the PV
panel 400 may also store energy during periods of high production
in the distribution system 120 and/or during period of higher than
nominal electrical output of the PV panel 400. The storage
subsystem 410 is further configured to retrieve the stored energy
and make the stored energy available to the PV panel 400. For
example, in response to unavailability or partial unavailability of
the insolation 108 or when called upon by an external
communication, the storage subsystem 410 may retrieve stored
energy. The energy made available by the storage subsystem 410 may
be adequate to maintain the nominal electrical output of the PV
panel 400 despite some variations in the insolation 108.
[0043] The storage subsystem 410 may be characterized by a holdup
time. The holdup time may indicate a particular duration in which
the storage subsystem 410 provides the nominal electrical output of
the PV panel 400 when the insolation 108 is completely unavailable.
For instance, the PV panel 400 may include a nominal electrical
output 110 Watts and the storage subsystem 410 may include a holdup
time may be about 15 minutes. The holdup time indicates the storage
subsystem 410 can maintain the nominal electrical output 110 Watts
of the PV panel 110 for 15 minutes in the absence of insolation
108.
[0044] The holdup time is determined by the size and capacity of
the storage subsystem 410. In some implementations, the holdup time
may be about 10 minutes. In other implementations, the holdup time
may be between about three hours and about five hours, for example.
In embodiments in which the holdup time is between about three
hours and about five hours, the storage subsystem 410 may provide
some percentage of (e.g., 85%) of the nominal electrical output of
the PV panel 400 for this period, which may enable some flexibility
in the PV panel 400 and the storage subsystem 410 for variations
due to transient obstructions 110 during this period.
[0045] In addition, the storage subsystem 410 may be configured to
store and provide more than the nominal electrical output. Some
embodiments of the storage subsystem 410 may provide between about
105% and about 300% of the nominal electrical output of the PV
panel 400. For example, the PV panel 400 may include a nominal
electrical output 110 Watts. The storage subsystem 410 may provide
an electrical output of between about 115 and about 330 Watts. The
electrical output of 330 Watts may be used in distribution grid
stabilization. For instance, to make up for failures or reductions
in production capacities in the distribution system 120.
[0046] The storage subsystem 410 provides per-panel energy storage.
As used in this disclosure, "per-panel" indicates that the storage
subsystem 410 is affiliated with the PV panel 400 and is not
affiliated with other PV panels that may be included in a panel
array that includes the PV panel 400. For instance, the storage
subsystem 410 receives electricity produced by the PV cells 104 of
the PV panel 400 and the storage subsystem 410 supplies energy
stored thereon to the PV output 106 of the PV panel 400.
[0047] Moreover, "per-panel" may indicate control of the electrical
output and input (e.g., in load-following applications) on a
per-panel basis. For example, instead of a global or centralized
control of an array that includes one or more of the PV panels 400,
the storage subsystem 410 includes functionality that is dedicated
to the control of the electrical output and input of the PV panel
400.
[0048] Generally, provision of per-panel energy storage enables
distribution of energy storage in a panel array. The distribution
of the energy storage enables efficient, rapid, and controllable
response to the transient obstructions 110. The response to the
transient obstructions 110 may smooth variability in the
distribution system 120. For example, an operator of the
distribution system 120 may control a ramp rate of the storage
device 422 (e.g., the percent of nameplate or nameplate
capacity/minute). The ramp rate may be controlled on a per-panel
basis.
[0049] A panel array that includes a number of the PV panels 100 of
FIGS. 1A and 1B without the storage subsystem 410 may require
centralized energy storage system. The centralized energy storage
system may store energy generated by multiple PV panels 100. The
centralized energy storage system may be a large-scale, independent
system (e.g., a hydraulic pump water storage or molten salt energy
storage). When the electrical output of the panel array is reduced,
the centralized energy storage system supplies energy to compensate
for the reduction. However, the centralized energy storage system
is large and complex and may not be able to mitigate electricity
production reductions within the short periods (e.g., about 10
minutes) in which the insolation 108 is unavailable or partially
unavailable.
[0050] In contrast, panel arrays with the PV panels 400 that use
the per-panel storage may accommodate for the transient
obstructions 110. The per-panel storage enables rapid mitigation of
electricity production reductions on a per-PV panel 400 basis.
Moreover, the individual PV panels 400 that are affected by the
transient obstructions 110 individually make up for any reductions
in local electricity production. In addition, inclusion of the
storage device 422 may reduce cooling costs when compared to
centralized energy storage systems and may eliminate a threat of a
single point of failure.
[0051] In some embodiments, the storage subsystem 410 is an
on-panel storage subsystem. As used in this disclosure, "on-panel"
indicates that the storage subsystem 410 is physically connected or
physically incorporated in the PV panel 400. For instance, the
storage subsystem 410 may be welded or fastened to a frame of the
PV panel. In other embodiments, the storage subsystem may not be
on-panel but may still provide per-panel energy storage.
[0052] The storage subsystem 410 is sized such that the nominal
output can be maintained for a particular duration. The particular
duration is either greater than a period of unavailability or
partial unavailability of the insolation 108 and/or greater than a
period involved in the initiation of another mitigation measure.
The storage subsystem 410 thus reduces disturbances to operation of
the distribution system 120 to which the PV panel 400 provides
electricity. In some embodiments, the particular duration may be
about 10 minutes. Some additional details of the particular
duration are discussed elsewhere herein.
[0053] In the embodiment of FIGS. 4A and 4B, the PV panel 400
includes the interconnected PV device string 102 that includes the
PV cells 104. The interconnected PV device string 102 is
electrically connected to the PV output 106. The PV cells 104 are
configured to photovoltaically generate an electric potential in
response to exposure to incident illumination. The incident
illumination is represented in FIGS. 4A and 4B by the insolation
108. A source of the insolation 108 is, in some embodiments, the
sun.
[0054] The PV output 106 may be electrically coupled to the
distribution system 120. The PV panel 400 may supply some portion
of the electricity produced by the PV cells 104 to the distribution
system 120 via the PV output 106. For example, during periods in
which the insolation 108 is available, a nominal output of the PV
panel 400, produced by the PV cells 104 may be supplied to the
distribution system 120. In addition, during periods in which the
insolation 108 is available, some portion of the energy produced by
the PV cells 104 may be provided to the storage subsystem 410 and
stored therein.
[0055] The storage subsystem 410 may be electrically coupled to the
interconnected PV device string 102. For example, in the depicted
embodiment, the storage subsystem 410 is electrically coupled in
parallel to the PV output 106. The storage subsystem 410 is
configured to receive some portion of the electricity produced by
the PV cells 104 while the insolation 108 is available and store
the electricity. In some embodiments, the storage subsystem 410 may
not store the electricity as electrical potential. For instance,
the storage subsystem 410 may include a dedicated energy storage
device (storage device) 422. The storage device 422 may include any
system or device that is capable of storage of energy and retrieval
of the stored energy to PV panel 400.
[0056] An example of the storage device 422 is a flywheel. Rotation
of the flywheel may be imposed due to electricity produced by the
PV cells 104. The rotation stores the electricity produced by the
PV cells 104 as kinetic energy. Another example of the storage
device 422 is an electrochemical battery. The electrochemical
battery may be charged by the electricity produced by the PV cells
104. Another example of the storage device 422 may include a
compressed gas system. The compressed gas system may use the
electricity produced by the PV cells 104 to impose a pressure on a
gas. The pressure stores the electricity produced by the PV cells
104 as pneumatic potential energy.
[0057] In addition, the storage subsystem 410 is configured to
supply stored energy in the form of electricity to the electrical
distribution system 120 via the PV output 106. For example, the PV
storage subsystem 410 may supply electricity to the distribution
system 120 while the insolation 108 is unavailable or partially
unavailable. For instance, FIG. 4B depicts the transient
obstruction 110 obscuring the insolation 108.
[0058] The amount of electricity supplied to the distribution
system 120 may be related to the effect on the PV panel 400 of the
unavailability or partial unavailability of the insolation 108. For
example, the storage subsystem 410 may supply electricity to the
distribution system 120 such that the nominal electrical output of
the PV panel 400 is constant or substantially constant. During
periods in which the storage subsystem 410 is supplying electricity
to the distribution system 120, the constant or substantially
constant nominal electrical output of the PV panel 400 may include
a first portion that results from electrical production of the PV
cells 104 and a second portion that is supplied from the storage
subsystem 410. Additionally, in some circumstances, the storage
subsystem 410 may supply all of the nominal electrical output of
the PV panel 400.
[0059] In some embodiments, the storage subsystem 410 may supply
electricity to the distribution system 120 outside of periods of
unavailability or partial unavailability of the insolation 108. For
example, during peak loads of the distribution system 120, the
storage subsystem 410 may supply electricity to the distribution
system 120. Additionally or alternatively, the storage subsystem
410 may supply electricity to the distribution system 120 in
response to an equipment failure or any other circumstance in which
additional electrical output may be beneficial.
[0060] An example of the PV panel 400 may include a nominal maximum
DC output power of 110 Watts at a nominal output voltage of 69.4
Volts and a nominal output current of 1.59 Amperes. In addition, in
FIGS. 4A and 4B, only one PV panel 400 is depicted. However, the PV
panel 400 may be incorporated into a panel array that includes
multiple PV panels 400. The panel array may include thousands of
the PV panel 400 as part of a large solar photovoltaic generation
facility.
[0061] Embodiments depicted in FIGS. 4A and 4B depict per-panel
implementations in which the PV panel 400 includes the storage
device 422. In some embodiments, the storage device 422 and the
storage subsystem 410 may be associated with a small number of PV
panels 400. For example, the storage device 422 and the storage
subsystem 410 may be associated with between two and ten PV panels
400. Generally, the PV panels 400 associated with the storage
device 422 and the storage subsystem 410 may be located physically
close to one another in a panel array.
[0062] FIG. 5 is an example plot 500 that depicts electrical output
of the PV panel 400 of FIGS. 4A and 4B. With combined reference to
FIGS. 4A-5, in FIG. 5, insolation energy flux per unit area is
plotted along a vertical axis 502. Time is plotted along a
horizontal axis 504. The insolation energy flux per unit area,
which may be in W/m.sup.2 and electrical output of the PV panel 400
are linearly related. Accordingly, the vertical axis 202 serves to
illustrate the relationship between both the electrical output and
the insolation energy flux per unit area during the depicted
events. The plot 500 includes the insolation line 206 discussed
with reference to FIG. 2. The plot 500 also includes an electrical
output line 510 and a storage subsystem output line 512. The
electrical output line 510 represents the net electrical output of
the PV panel 400. The storage subsystem output line 512 represents
energy output of the storage subsystem 410.
[0063] The plot 500 may be separated into four time periods 520,
522, 524, and 526. A first time period 520 is from time equal to 0
on the plot 500 until a first time 528. The first time 528
represents an onset of insolation reduction.
[0064] The first time period 520 is representative of circumstances
in which the insolation 108 is available and the storage device 422
of the storage subsystem 410 is substantially full or has reached a
limit determined by a customer. During the first time period 520,
the electrical output of the PV panel 400 is substantially
constant. The electrical output is supplied by electricity produced
by the PV cells 104 (of FIGS. 4A and 4B). There may be some output
by the storage subsystem 410. The output by the storage subsystem
410 may be supplying components (e.g., providing power to a
controller) of the storage subsystem 410, for instance.
[0065] A second time period 522 is from the first time 528 until a
second time 530. The second time 530 represents cessation of the
insolation reduction. During the second time period 522, the
insolation 108 may be considered unavailable or partially
unavailable. In some embodiments, the insolation 108 is considered
unavailable or partially unavailable when the nominal electrical
output of the PV panel 400 supplied by the PV cells 104 is
decreased by more than about 10%. Similarly, the insolation 108 may
be considered available so long as about 90% the nominal electrical
output of the PV panel 400 is supplied by the PV cells 104.
[0066] During the second time period 522, the energy output of the
storage subsystem 410 increases relative to a reduction in the
insolation 108 such that the electrical output of the PV panel 400
is substantially constant.
[0067] A third time period 524 is from the second time 530 until a
third time 532. The third time 532 represents a time in which
electricity produced by the PV cells 104 is supplied to the storage
subsystem 410. During the third time period 524, some amount of
energy may be supplied by the storage subsystem 410. However, the
electrical output of the PV panel 400 is supplied by the
electricity produced by the PV cells 104.
[0068] A fourth time period 526 is from the third time 532 until a
fourth time 534. The fourth time 534 represents a time in which the
storage device 422 of the storage subsystem 410 is full. During the
fourth time period 526, the electrical output of the PV panel 400
is supplied by electricity produced by the PV cells 104. In
addition, electricity produced by the PV cells 104 is being stored
in the storage subsystem 410. In the plot 500, the portion of
storage subsystem output line 512 below the horizontal axis 504
represents charging or energy storage.
[0069] On the plot 500, the electrical output line 510 is
substantially constant. In some embodiments, during the second time
period 522, the electrical output line 510 may be somewhat lower.
In these and other embodiments, the electrical output line 510 may
be a step function beginning at the first time 528 and ending at
the second time 530. For example, the electrical output line 510
may be constant during the first time period 520, the third time
period 524, and the fourth time period 526. During the second time
period 522, the electrical output line 510 may be about 80% of the
value during the first time period 520, the third time period 524,
and the fourth time period 526.
[0070] FIG. 6 illustrates an example PV assembly 600 that includes
an embodiment of the PV panel 400. FIG. 6 depicts a sectional view
of the PV assembly 600. The PV assembly 600 is depicted mounted on
the ground 602 with the storage subsystem 410 mounted partially
below a surface of the ground 602. The PV panel 400 may be mounted
to a frame 608, which is positioned on the ground 602. The frame
608 supports the PV panel 400 above the ground 602 and may
physically contain an enclosure 610. The storage subsystem 410 or
some portion thereof is positioned in the enclosure 610. For
example, in the embodiment of FIG. 6, the storage device 422 is
positioned within the enclosure 610.
[0071] In FIG. 6, the enclosure 610 is partially below the ground
602. The enclosure 610 may be positioned below the ground 602 to
reduce damage if the storage device 422 fails. For instance, the
storage device 422 may include a flywheel that stores energy in
inertia. The flywheel may rotate at a high rotation per minute
(RPM). For example, the flywheel may rotate at about 70,000 to
about 90,000 RPM. If there is a mechanical failure, the flywheel or
components thereof may become disconnected and may damage other
components of the PV assembly 600. By positioning the enclosure 610
at least partially below the ground 602, any damage caused by
failure of the flywheel may be reduced.
[0072] The insolation 108 may impinge on a surface 604 of the PV
panel 400. The insolation 108 may result in production of
electricity that is communicated via a connection 606 to PV panel
output connection cables 612. The PV panel output connection cables
612 connect to a series connection 614. The series connection 614
may be an example of the PV output 106 discussed above. The series
connection 614 may electrically connect to another PV assembly
and/or to a distribution system (e.g., the distribution system 120
discussed above). The series connection 614 may be positioned in a
cable run enclosure 616.
[0073] In some embodiments, multiple (e.g., 1000) PV assemblies 600
are installed in series. The cable run enclosure 616 may be
constructed below the multiple PV assemblies 600. A cable that
connects the PV assemblies 600 may be positioned above the cable
run enclosure 616. Each of the PV assemblies 600 may be connected
to the cable at the series connection 614.
[0074] The PV panel output connection cables 612 connect to storage
device connections 618 via panel/storage device connections 620.
When the insolation 108 is available, a first portion of the
electricity produced by PV cells 104 (not shown) in the PV panel
400 is supplied to the series connection 614. A second portion of
the electricity produced by the PV cells 104 is supplied to the
storage device 422 via the panel/storage device connections 620 and
the storage device connections 618. In response to the insolation
108 being unavailable or partially unavailable, energy stored in
the storage device 422 may be supplied to the series connection 614
via the storage device connections 618 and the panel/storage device
connections 620.
[0075] As depicted in FIG. 6, the PV assembly 600 includes the
storage device 422. The storage device 422 included in the PV
assembly 600 is an example of on-panel storage. The storage device
422 is integrated in the PV assembly 600. In systems including
multiple PV assemblies 600, each of the PV assemblies 600 may
include the on-panel storage as depicted in FIG. 6. In other
embodiments, the enclosure 610 in which the storage device 422 is
positioned may be located away from the PV panel 400. In these and
other embodiments, the storage device 422 may provide per-panel
storage.
[0076] FIG. 7 illustrates an example embodiment of the storage
subsystem 410. The storage subsystem 410 is depicted electrically
coupled between the PV device string 102 of the PV panel 400 and
the distribution system 120 discussed elsewhere in this disclosure.
The storage subsystem 410 of FIG. 7 is an example of an on-panel
storage subsystem. In addition to the functionality discussed
elsewhere in this disclosure, the storage subsystem 410 provides
per-panel energy storage management functionality.
[0077] For example, the storage subsystem 410 manages supply of the
electricity produced by the PV device string 102 to the energy
storage device 422. In addition, the storage subsystem 410 manages
the energy retrieval from the storage device 422 and its supply to
the distribution system 120. In some embodiments, the storage
subsystem 410 may further manage energy provided by the
distribution system 120 to the storage device 422.
[0078] The storage subsystem 410 of FIG. 7 may include the energy
storage device 422, a maximum power point transfer (MPPT) device
702, an inverter 704, a controller 708, a communication unit 714,
or some combination thereof. The controller 708 may enable a
customer to define a particular behavior of the PV panel 400. The
controller 708 may be programmed for allocation of energy between
the storage device 422 and the distribution system 120. For
example, a customer may set ramp rates, rates at which energy is
absorbed by the storage device 422, an amount to which the storage
device 422 is charged, define panel behavior based on environmental
or grid load circumstances, set an electrical output of the PV
panel 400 (e.g., a substantially constant electrical output), set
an electrical output reduction rate (e.g., reduction of 1% per
minute), or some combination thereof.
[0079] The controller 708 may also communicate signals to one or
more of the communication unit 714, the MPPT 702, the inverter 704,
the energy storage device 422, or some combination thereof. For
example, the controller 708 may receive a signal indicative of a
reduction in electricity output from the PV device string 102, and
the controller 708 may then communicate a control signal that
commands the inverter to pull energy from the storage device
422.
[0080] In the depicted embodiment, the controller 708 may include
one or more processors 710 and memory 712. The processor 710 may
include any suitable special-purpose or general-purpose computer,
computing entity, or processing device including various computer
hardware or software modules and may be configured to execute
instructions stored on any applicable computer-readable storage
media. For example, the processor 710 may include a microprocessor,
a microcontroller, a digital signal processor (DSP), an
application-specific integrated circuit (ASIC), a
field-programmable gate array (FPGA), or any other digital or
analog circuitry configured to interpret and/or to execute program
instructions and/or to process data.
[0081] Although illustrated as a single processor in FIG. 7, the
processor 710 may more generally include any number of processors
configured to perform individually or collectively any number of
operations described in the present disclosure. Additionally, one
or more of the processors 710 may be present on one or more
different electronic devices or computing systems. In some
embodiments, the processor 710 may interpret and/or execute program
instructions and/or process data stored in the memory 712 or other
data storage. In some embodiments, the processor 710 may fetch
program instructions from the memory 712 and load the program
instructions. After the program instructions are loaded, the
processor 710 may execute the program instructions.
[0082] The memory 712 may include computer-readable storage media
for carrying or having computer-executable instructions or data
structures stored thereon. Such computer-readable storage media may
include any available media that may be accessed by a
general-purpose or special-purpose computer, such as the processor
710. By way of example, and not limitation, such computer-readable
storage media may include tangible or non-transitory
computer-readable storage media including RAM, ROM, EEPROM, CD-ROM
or other optical disk storage, magnetic disk storage or other
magnetic storage devices, flash memory devices (e.g., solid state
memory devices), or any other storage medium which may be used to
carry or store desired program code in the form of
computer-executable instructions or data structures and that may be
accessed by a general-purpose or special-purpose computer.
Combinations of the above may also be included within the scope of
computer-readable storage media. Computer-executable instructions
may include, for example, instructions and data configured to cause
the processor 710 to perform a certain operation or group of
operations.
[0083] In the embodiment depicted in FIG. 7, the storage subsystem
410 includes the controller 708. These and other embodiments may
include a configuration that includes one controller (e.g., 708)
per panel. In these and other embodiments, the controller 708 is
dedicated to the PV panel in which it is implemented. Accordingly
in an array including multiple PV panels having a one controller
per panel configuration, there may not be a global controller that
determines the output and input of individualized PV panels. A lack
of a global controller may eliminate or reduce single-point failure
vulnerabilities in the array.
[0084] The communication unit 714 may include one or more pieces of
hardware configured to receive and send communications. In some
embodiments, the communication unit 714 may include one or more of
an antenna, a wired port, and modulation/demodulation hardware,
among other communication hardware devices. In particular, the
communication unit 714 may be configured to receive a communication
from outside the PV panel 400 and to present the communication to
the processor 710 or to send a communication from the processor 710
to another device or network.
[0085] In some embodiments, the communication unit 714 may be
configured to communicate status signals pertaining to operations
of the PV panel 400. For example, the communication unit 714 may be
configured to input/output signals informing a grid manager of an
operational status (e.g., state of the charge) of the PV panel 400.
Additionally, new programs or changes to instructions may be
communicated to the controller 708 via the communication unit
714.
[0086] In embodiments including the controller 708 and the
communication unit 714, a program may be preset to the controller
708. Control communications may be received by the communication
unit 714, which may modify or overwrite the preset program.
[0087] In some embodiments, the storage subsystem 410 may include
the communication unit 714 but omit the controller 708. In these
and other embodiments, the storage subsystem 410 may receive
control communications that are directly communicated to one or
more of the energy storage device 422, the MPPT device 702, and the
inverter 704.
[0088] The MPPT device 702 may be electrically coupled to the PV
device string 102, the controller 708, and the inverter 704. The
MPPT device 702 may be configured to perform MPPT techniques. For
example, the MPPT device 702 may be configured to determine an
optimal current-voltage (IV) point. The IV point may change due to
environmental conditions such as temperature, insolation, and the
like.
[0089] The inverter 704 may receive a signal from the controller
708 and in response draw energy from the storage device 422. The
inverter 704 may convert energy drawn from the storage device 422
and the PV device string 102 from direct current (DC) to
alternating current (AC). The inverter 704 may then communicate the
electricity converted to AC to the PV output 106.
[0090] The inverter 704 may be a bi-directional inverter. In
embodiments in which the inverter 704 is bi-directional,
electricity may be drawn from the distribution system 120. For
example, in circumstances in which the energy production in the
distribution system 120 exceeds a load in the distribution system
120, electricity may be drawn from the distribution system 120 and
stored in the storage device 422. The electricity may be drawn from
the distribution system 120. The electricity is then converted from
AC to DC and supplied to the storage device 422.
[0091] For example, in some embodiments, the storage device 422 may
be set to only charge or store about 50% to about 60% of a
designed-for capacity. During periods in which energy generation on
the grid is high (more than load), excess electricity is stored on
the storage device 422. Storage of the excess electricity is
referred to as "load following."
[0092] In some embodiments, the storage subsystem 410 of FIG. 7 may
include an energy dissipator such as a resistor. If adequate energy
storage capacity is not available in the storage device 422 to
store the entire amount of energy involved by load following
corrective measures, then the storage subsystem 410 may dissipate
excess energy through the dissipater.
[0093] Furthermore, the inverter 704 may controllably alter its AC
output parameters, including voltage, current, frequency, phase,
harmonic content, or any combination thereof. Such alterations may
be in response to commands generated off-panel and received by
communications unit 714, or in response to algorithms executed by
the processor 710, or a combination thereof.
[0094] FIG. 8 depicts another example embodiment of the storage
subsystem 410 that may be implemented in the PV panel 400. The
embodiment of FIG. 8 includes a simple embodiment of per-panel
energy storage implemented with the PV panel 400. The PV panel 400
includes a storage device 422 that includes a rechargeable
electrochemical storage device (battery) 802. The battery 802 is
electrically coupled to the PV device string 102. The battery 802
is configured to maintain and/or stabilize electrical output of the
PV panel 400 as discussed elsewhere in this disclosure.
[0095] In the embodiment of FIG. 8, the storage subsystem 410 that
provides per-panel storage to the PV panel 400 is on-panel. In
other embodiments, the storage subsystem 410 may be off-panel. The
battery 802 may include active or passive temperature control such
as thermal insulation, temperature control by thermally driven
phase change of materials, or temperature control by thermoelectric
devices.
[0096] In the embodiment depicted in FIG. 8, the storage subsystem
410 incorporates battery management electronics 804 that operate
the electrochemical cells of the battery 802 within safe limits.
For example, the battery management electronics 804 may operate the
electrochemical cells regarding aspects of charge, discharge, cell
state of charge balance, depth of discharge, fault mitigation, and
other parameters.
[0097] In the embodiment depicted in FIG. 8, when electrical energy
produced by the PV device string 102 decreases below a voltage of
the battery 802, the electrical output available at PV output 106
declines until it is approximately equal to the voltage exhibited
by the battery 802. The voltage exhibited by the battery 802 may be
determined by the state of charge, temperature, and voltage
drops.
[0098] An isolation diode 806 may be incorporated within the
storage subsystem 410 and its battery management electronics. Upon
the electrical output at the PV output 106 being about equal to or
less than the charge of the battery 802, the battery 802 begins to
supply electrical energy to the PV output 106. The amount of
electrical energy supplied to the PV output 106 may be related to a
difference between electrical output and the charge of the battery
802. The battery 802 continues to supply electrical energy to the
PV output 106 until insolation 108 is available and the electrical
output of the PV panel 400 rises above the charge of the battery
802 or the battery 802 is fully discharged.
[0099] In some embodiments, a predetermined portion of electrical
energy produced by the PV device string 102 may be used to recharge
the battery 802 while continuing to supply energy to the PV output
106.
[0100] In contrast with the embodiment of FIG. 7, the embodiment of
FIG. 8 is very simple. The embodiment of FIG. 8 may omit components
for communications, computation, DC/AC conversion, or other
electronic functionalities. Additionally, in some embodiments the
MPPT 702 may be further omitted. Instead, the embodiment of FIG. 8
includes battery management electronics 804 and isolation diode 806
used to stabilize the electrical output of the PV panel 400.
[0101] In a non-depicted embodiment, the storage device 422 may
include a flywheel assembly with its integral operational control
electronics in close analogy to the embodiment of FIG. 8.
Additionally, the storage device 422 may include multiple storage
devices 422, each incorporating its particular storage management
functionality. In some embodiments, the PV panel 400 may include
the MPPT device 702. The MPPT device 702 operates to maintain the
electrical output of the PV panel 400 at a maximum possible under
operating conditions that determine the IV curve of the PV panel
400. The operating conditions may include temperature, insolation,
and the particular technology employed for manufacture of the PV
panel 400. The MPPT device 702 may employ algorithms such as
perturb and observe algorithm, hill climbing algorithm, incremental
conductance algorithm, current sweep algorithm, or constant voltage
algorithm. The MPPT device 702 resides in a physical device
dedicated solely to MPPT operations or may be integrated into other
devices. The MPPT device 702 may be easily retrofitted to the PV
panel 400.
[0102] FIG. 9 illustrates an example embodiment of the storage
device 422. In the embodiment of FIG. 9, the storage device 422
includes a flywheel assembly 900. The flywheel assembly 900 of FIG.
9 may be electrically coupled to a PV device string such as the PV
device string 102 and to a PV output such as the PV output 106
described elsewhere in this disclosure. The flywheel assembly 900
is configured to maintain and/or stabilize electrical output of a
PV panel including the flywheel assembly 900 as discussed elsewhere
in this disclosure.
[0103] The flywheel assembly 900 may be configured with a larger
energy storage range and larger energy retrieval range than battery
802 of FIG. 8. For example, the flywheel assembly 900 may provide
electrical energy output that exceeds a nominal energy output of a
PV panel or without damaging the flywheel assembly 900. When
compared to the battery of 802 of FIG. 8, the flywheel assembly 900
may be configured with a larger energy storage rate, storage power
and larger energy retrieval rate, retrieval power, or some
combination thereof.
[0104] The flywheel assembly 900 may include a flywheel rotor 902
that is positioned within an evacuated enclosure 904. In some
embodiments, the flywheel rotor 902 may be comprised of a carbon
fiber matrix composite material. The carbon fiber may include any
suitable material such as M30 product from Toray Carbon Fibers
America, Inc. The carbon fiber matrix may be a polymeric form of
dicyclopentadiene (DCPD) polymerized according to metathesis
reactions, for instance. In other embodiments, the flywheel rotor
902 may be comprised of another material or another polymeric
form.
[0105] In the embodiment of FIG. 9, the flywheel rotor 902 may have
an outer diameter 906 of about 5 inches, an inner diameter 908 of
about 10 millimeters, and a nominal thickness (in FIG. 9, extent in
an arbitrarily defined z-direction) of about 1.0 inch. The flywheel
rotor 902 may include about 1.25 pounds of carbon fiber M30. The
carbon fiber M30 is circumferentially wrapped in the flywheel rotor
902 with a winding inclination or pitch of about 5.degree. with
respect to the planar end faces of the flywheel rotor 902.
[0106] Two circular arrays of magnets (magnet arrays) 910A and 910B
are imbedded in the flywheel rotor 902. The arrays of magnets 910A
and 910B may be disposed in the flywheel rotor 902 during the
fabrication of the flywheel rotor 902. The arrays of magnets 910A
and 910B rotate with the flywheel rotor 902 and project magnetic
fields across the enclosure 904 to interact, respectively, with
electromagnetic coil assemblies 912A and 912B. The magnet arrays
910A and 910B may include N42 grade rare earth magnets. One or more
individual magnets of magnet arrays 910A and 910B may include a
nickel-plated cube. The magnets may include an edge length of about
0.5 inches.
[0107] The magnet arrays 910A and 910B are distributed on a top
face and a bottom face of flywheel rotor 902. Array centerline
radii 916 and 918 may be at about 1.75 inches and about 2.35 inches
from a central rotational axis 914 of flywheel rotor 902. The
magnets of the magnet arrays 910A and 910B are angularly displaced
from its adjacent neighbors by approximately 20 degrees. In the
depicted embodiment, the magnet arrays 910A and 910B include
eighteen magnets. The flywheel rotor 902 may include fifty-two
magnets total. In other embodiments the magnet arrays 910A and 910B
may include fewer than eighteen or more than eighteen magnets.
Additionally, the magnet arrays 910A and 910B may be positioned at
different centerline radii 916 and 918. Other embodiments may
include other types or dispositions of magnets and other operative
configurations such as an arrangement of magnet polarities in a
Halbach configuration as well as magnets of other geometries, and
other rare earth magnet grades.
[0108] The electromagnetic coil assemblies 912A and 912B may
include multiple coils. For example, in an example embodiment, the
electromagnetic coil assemblies 912A and 912B may include twelve
coils with fifteen turns of #22 insulated copper magnet wire. Each
of the coils includes an approximate major diameter of about 1.0
inch. The twelve coils are disposed in a circular pattern and fixed
to an outside surface of the enclosure 904, with each of the coils
being centered at a radius of about 2.0 inches from a radial center
of the enclosure 904. The coils may be positioned on the enclosure
904 at regularly spaced angular positions separated by about 20
degrees around the enclosure 904.
[0109] To store energy within the flywheel assembly 900, the
electromagnetic coil assemblies 912A and 912B are electrically
connected to drive electronics (not depicted) that supply the
electromagnetic coil assemblies 912A and 912B with electrical
energy. Forces arise from the interaction of electromagnetic fields
created by the electromagnetic coil assemblies 912A and 912B with
permanent magnetic fields provided by the magnet arrays 910A and
910B. The forces cause the flywheel rotor 902 to increase a
rotation rate, thereby effecting the conversion of electrical
energy supplied to the electromagnetic coil assemblies 912A and
912B. Increasing the rotation rate increases rotational kinetic
energy of the flywheel rotor 902.
[0110] To recover electrical energy from the flywheel assembly 900,
induced current is driven by the relative motion of electromagnetic
coil assemblies 912A and 912B to the magnetic fields from rotating
magnet arrays 910A and 910B. The electromagnetic coil assemblies
912A and 912B to a PV output (e.g., the PV output 106) after being
transformed and/or rectified according to whether panel output is
required as AC or DC power. Rotational kinetic energy is thereby
transformed to electrical energy in accordance with principles of
electric generators.
[0111] The inner diameter 908 of flywheel rotor 902 is mechanically
fixed to a shaft 920. The shaft 920 may include a diameter of about
0.500 inch and may be comprised of stainless steel. The flywheel
rotor 902 is wound onto the shaft 920 so that in operation, the two
components rotate together as an integrated assembly. The shaft 920
may be constructed from stainless steel alloy 316 or similar alloys
having a relative magnetic permeability of less than about 100. The
shaft 920 may be comprised of other materials having similar
magnetic and mechanical properties. Examples of such shaft
materials may include titanium, silicon carbide, and cermet
compositions. Additionally, in some embodiments, rather than
winding the flywheel rotor 902 material directly on the shaft 920.
For example, an interface component (not depicted) may be installed
between the flywheel rotor 902 and the shaft 920 to provide
advantageous mechanical properties, such as enhanced compliance
and/or energy dissipation (damping).
[0112] In the embodiment of FIG. 9, the flywheel rotor 902 and the
shaft 920 comprise a rotating assembly. The rotating assembly is
radially located by a first passive magnetic bearing and a second
passive magnetic bearing. The first passive magnetic bearing
includes mutually repulsive cylindrical magnet components
(repulsive magnets) 934A and 932A. The second passive magnetic
bearing includes repulsive magnets 934B and 932B. The repulsive
magnets 932A, 932B, 934A, and 934B are axially magnetized. For
example, the North and South poles are located on the parallel,
planar magnet end faces and the magnetization axis is parallel to
the cylindrical axis 914. In FIG. 9, each of the repulsive magnets
932A, 932B, 934A, and 934B include arrows indicating an orientation
of the North and South poles.
[0113] The repulsive magnets 932A, 932B, 934A, and 934B are
oriented so that the radial interaction is repulsive. In addition,
radial equilibrium positions occur when the repulsive magnets 932A
and 932B are radially and axially centered within the repulsive
magnets 934A and 934B, respectively. The repulsive magnets 932A and
932B are fixed to the shaft 920. The repulsive magnets 934A and
934B are fixed to enclosure 904. For example, one or more of the
repulsive magnets 932A, 932B, 934A, and 934B may be fixed using J-B
Weld.RTM. product #8265-S or a similar, suitable adhesive.
[0114] In some embodiments, one or more of the repulsive magnets
932A, 932B, 934A, and 934B are comprised of rare earth grade 42.
Additionally, in some embodiments, the repulsive magnets 932A and
932B may have inside diameters of about 0.500 inch, outer diameters
of about 1.0 inch, and thicknesses (heights) of about 0.5 inches.
The repulsive magnets 934A and 934B may have inside diameters of
about 0.750 inches, outer diameters of about 1.5 inches, and
thicknesses (heights) of about 0.250 inches.
[0115] In some embodiments, the passive radial magnetic bearings
may include a different structure or orientation. For example, a
Halbach magnet array, radially magnetized rings, or rings assembled
using magnets shaped as segments of a desired assembled ring may be
implemented in the flywheel assembly 900 of FIG. 9.
[0116] Wear elements 926A, 926B, 928A, 928B, 930A, and 930B fix the
axial position of the flywheel rotor 902 and the shaft 920. For
example, mechanical interaction of wear elements 926A, 928A, and
930A fix a first end of the shaft 920 and mechanical interaction of
wear elements 926B, 928B, and 930B fix a second, opposite end of
the shaft 920. Together, the wear elements 926A, 928A, 930A, 926B,
928B, and 930B act as axial or thrust bearings that constrain the
axial position of the flywheel rotor 902 and the shaft 920.
[0117] The wear elements 926A, 926B, 928A, 928B, 930A, and 930B are
manufactured from a wear resistant material. For example, the wear
resistant material includes about 95% by volume diamond dust and
about 5% metallic binder. Upon treatment with heat and pressure,
the metallic binder consolidates the diamond dust into a hard,
wear-resistant material that may subsequently be formed and
polished to desired shape.
[0118] In some embodiments, the wear elements 926A and 926B are
plane-parallel discs. The wear elements 926A and 926B may have a
diameter of about 0.49 inches and a thickness of about 2.00
millimeters. Opposed faces of the wear elements 926A and 926B may
be polished to an average roughness of less than 0.10 microns. One
of the wear elements 926A and 926B may be mechanically fixed to
each end of shaft 920 prior to rotation. For example, the wear
elements 926A and 926B may be brazed to its corresponding position
on shaft 920 using a titanium-activated braze. Prior to final
assembly, the exposed surfaces of the wear elements 926A and 926B
may be coated with a vacuum-compatible solid lubricant (e.g.,
Molykote.RTM. Z powder).
[0119] The wear elements 928A and 928B are spheres. The wear
elements 928A and 928B may be comprised of Element Six type CTM302
PCD material. In some embodiments, the wear elements 928A and 928B
may have radii of about 3.0 millimeters and an average surface
roughness less than 0.10 microns. The wear elements 928A and 928B
may be coated with a vacuum-compatible solid lubricant prior to
assembly. The wear elements 928A and 928B run in or spin briefly in
their locating depressions in the wear elements 930A and 930B prior
to assembly.
[0120] The wear elements 930A and 930B are discs. The wear elements
930A and 930B may be comprised of Element Six type CTM302 PCD
material. In some embodiments, the wear elements 930A and 930B may
have a diameter of about 0.625 inches and a thickness of about 2
millimeters. One face of each of the wear elements 930A and 930B
may be planar and polished to an average surface roughness of less
than 0.10 microns. An opposite face of each of the wear elements
930A and 930B is similarly planar and polished to an average
surface roughness of less than 0.10 microns.
[0121] A spherical depression is defined in the wear elements 930A
and 930B. In some embodiments, the depth of the depression may be
about 2.00 millimeters and the radius of the depression may be not
less than about 3.00 millimeters. Each depression is centered on
the face in which it is formed and may have an average surface
roughness of less than about 0.10 microns.
[0122] The wear elements 930A and 930B are attached to their
respective locations on the inner surface of enclosure 904 by
adhesive bonding. For example, the wear elements 930A and 930B may
be adhered to the enclosure 904 using J-B Weld.RTM. #8265-S
adhesive or a similar product. Prior to assembly, each spherical
depression may be coated with a vacuum-compatible solid lubricant.
The wear elements 930A and 930B may be subjected to a brief
run-in.
[0123] In some embodiments, the axial location and thrust bearing
functionality of the flywheel assembly 900 may be obtained with
other wear-resistant materials such as silicon carbide, tungsten
carbide, synthetic diamond, other appropriate materials, or some
combination thereof. As well, some embodiments include providing
the axial location and thrust bearing functionality through use of
other types of bearings, such as conical (tapered) roller bearings
and thrust bearings comprised of planar surfaces separated by
rolling elements.
[0124] Moreover, some embodiments use of interface or attachment
materials that provide compliance and/or energy damping. The
interface or attachment materials may be advantageous for a
specific design with respect to rotor dynamics, stability,
vibration control, or wear lifer. For example, wear elements 930A
and 930B may be fixed to enclosure 904 using pads of compliant
material placed between the wear elements and the enclosure
surface. The pads of compliant material may provide compliance
and/or energy dissipation. An example of using a compliant material
is interposition of a layer of silicon rubber having a thickness of
about 1/16 inches and a Durometer hardness of 50 A between each of
the wear elements 930A and 930B and their corresponding locations
on enclosure 904. A suitable elastomer material is silicone rubber.
A suitable adhesive for bonding silicon rubber between the
enclosure 904 and the wear elements 930A or 930B may include an
adhesive tape (e.g., 3M.TM. Adhesive Transfer Tape type
7955MP).
[0125] FIG. 10 illustrates an example embodiment of the storage
device 422. In the embodiment of FIG. 10, the storage device 422
includes a flywheel assembly 1000. The flywheel assembly 1000 of
FIG. 10 may be electrically coupled to a PV device string such as
the PV device string 102 and to a PV output such as the PV output
106 described elsewhere in this disclosure. The flywheel assembly
1000 is configured to maintain and/or stabilize electrical output
of a PV panel including the flywheel assembly 1000 as discussed
elsewhere in this disclosure.
[0126] The flywheel assembly 1000 is similar to the flywheel
assembly 900 described with reference to FIG. 9. For example, the
flywheel assembly 1000 includes the flywheel rotor 902 that is
connected to the shaft 920 and positioned in the enclosure 904. The
enclosure 904 is evacuated. Energy storage and energy retrieval is
accomplished using the arrays of magnets 910A and 910B and the
electromagnetic coil assemblies 912A and 912B as described
elsewhere in this disclosure. Some embodiments of the flywheel
assembly 1000 may be sized similarly to the flywheel assembly 900
of FIG. 9 and may be comprised of similar materials.
[0127] The flywheel assembly 1000 includes roller element bearings
1002A and 1002B. The roller element bearings 1002A and 1002B
provide mechanical support and spin isolation for the flywheel
rotor 902. The roller element bearings 1002A and 1002B are
positioned between the shaft 920 and a rotor bearing interface
1004. In some embodiments, the roller element bearings 1002A and
1002B may be attached to the shaft 920 or the rotor bearing
interface 1004.
[0128] The rotor bearing interface 1004 provides a mechanical
interface between the outer surfaces of roller element bearings
1002A and 1002B and the flywheel rotor 902. The rotor bearing
interface 1004 may be comprised of materials such as elastomers
that provide compliance and/or damping.
[0129] The flywheel assembly 1000 also includes capture components
1006A and 1006B. The capture components 1006A and 1006B provide a
mechanical interface between shaft 920 and locations on the inner
surface of the enclosure 904. The capture components 1006A and
1006B may be comprised of materials such as elastomers that provide
compliance and/or damping.
[0130] FIGS. 11A-11C illustrate a block diagram of another example
embodiment of the storage device 422. The embodiment of FIGS.
11A-11C includes a flywheel assembly 1100. In particular, FIG. 11A
depicts a sectional view of the flywheel assembly 1100. FIG. 11B
depicts a top view of the flywheel assembly 1100. FIG. 11C depicts
a bottom view of the flywheel assembly 1100.
[0131] The flywheel assembly 1100 of FIGS. 11A-11C may be
electrically coupled to a PV device string such as the PV device
string 102 and to a PV output such as the PV output 106 described
elsewhere in this disclosure. The flywheel assembly 1100 is
configured to maintain and/or stabilize electrical output of a PV
panel including the flywheel assembly 1100 as discussed elsewhere
in this disclosure. The flywheel assembly 1100 includes active
magnetic rotor position control.
[0132] The flywheel assembly 1100 is a per-panel storage device
that includes an enclosure 1103. The enclosure 1103 is similar to
the enclosure 904 described above. For example, the enclosure 1103
is evacuated such that a vacuum or partial vacuum is formed within
the enclosure 1103. The vacuum reduces resistance to rotation of a
flywheel rotor 1105. The flywheel rotor 1105 is similar to the
flywheel rotor 902 in material construction. The flywheel rotor
1105 is placed in the enclosure 1103. During operation, the
flywheel rotor 1105 is positioned by electromagnetic actuators.
Positioning the flywheel rotor 1105 reduces or eliminates wear
incident to mechanical bearings.
[0133] Referring to FIG. 11A, the flywheel rotor 1105 rotates about
a rotational axis 1107 that is parallel to an arbitrarily defined
z-axis. During installation, the flywheel assembly 1100 is leveled
substantially perpendicular with respect to local gravitational
vector 1108. For example, the rotational axis 1107 may be
substantially perpendicular to the x-axis of FIG. 11A. In some
embodiments, the flywheel assembly 1100 may be leveled to within
approximately 0.5.degree. of perpendicular and in other embodiments
to less than 0.1.degree. of perpendicular. Leveling the flywheel
assembly 1110 may be performed by adjustment of the mechanical
structure (not shown) that supports enclosure 904.
[0134] Referring to FIGS. 11A-11C, the flywheel rotor 1105 may
include ferromagnetic elements 1102A and 1102B. The ferromagnetic
elements 1102A and 1102B may be incorporated within the flywheel
rotor 1105 during its fabrication. The ferromagnetic elements 1102A
and 1102B may be comprised of thin annular strips or rings of
ferromagnetic material. For example, in the depicted flywheel
assembly 1100, the ferromagnetic elements 1102A and 1102B may be
constructed of 1018 alloy steel. Additionally in this and other
embodiments, the ferromagnetic elements 1102A and 1102B may have a
thickness of 0.010 inches, an inside diameter of 4.50 inches, and
an outer diameter of 5.00 inches.
[0135] The ferromagnetic elements 1102A and 1102B may be adherently
bonded to the depicted upper and lower planar surfaces,
respectively, of the flywheel rotor 1105 after winding and
finishing operations. Additionally or alternatively, the
ferromagnetic elements 1102A and 1102B may be incorporated within
the body of the flywheel rotor 1105 during winding operations. In
embodiments in which the ferromagnetic elements 1102A and 1102B are
incorporated within the body of the flywheel rotor 1105 they are
embedded within the flywheel rotor 1105.
[0136] The flywheel rotor 1105 may also include a ferromagnetic
element 1104. The ferromagnetic element 1104 may be incorporated
within the flywheel rotor 1105 during its fabrication. The
ferromagnetic element 1104 may be comprised of a strip of
ferromagnetic material. For example, in the depicted flywheel
assembly 1100, the ferromagnetic element 1104 includes a
circumferential strip of 1018 alloy steel. In this and other
embodiments, the ferromagnetic element 1104 may have a thickness of
about 0.010 inches, a width (Z-axial extent) of about 0.5 inches,
and an average radius of about 4.50 inches. The ferromagnetic
element 1104 may be incorporated within the rotor structure during
manufacture, which may result in the ferromagnetic element 1104
being embedded within the body of the flywheel rotor 1105.
Additionally or alternatively, the ferromagnetic element 1104 may
be adherently bonded to an outer cylindrical surface of the
flywheel rotor 1105 after rotor winding and finishing
operations.
[0137] As best depicted in FIG. 11B, the flywheel assembly 1100
also includes two ferromagnetic position sensors 1106A and 1106B.
The ferromagnetic position sensors 1106A and 1106B are fixed to the
upper outer surface of the enclosure 1103. The ferromagnetic
position sensors 1106A and 1106B may include inductive-proximity
sensors (e.g., Eaton Cutler Hammer Inductive Proximity Sensor
E57).
[0138] Referring back to FIGS. 11A-11C, the flywheel assembly 1100
includes sensors 1110, 1106A, 1106B, 1112A, and 1112B. The sensors
1110, 1106A, 1106B, 1112A, and 1112B provide data that enable
computation of the position of the flywheel rotor 1105 with respect
to the enclosure 1103. The position of the flywheel rotor 1105 with
respect to enclosure 1103 is used to maintain physical clearance
between the flywheel rotor 1105 and the enclosure 1103 during
operation. For example, when data measured by the sensors 1110,
1106A, 1106B, 1112A, and 1112B indicate the flywheel rotor 1105 may
hit the enclosure 1103, a corrective signal is generated that
re-position the flywheel rotor 1105 relative to the enclosure
1103.
[0139] The flywheel assembly 1100 includes the ferromagnetic
position sensors 1106A and 1106B that are positioned opposite the
ferromagnetic element 1102A. For example, a first ferromagnetic
position sensor 1106A is positioned on an axis that is parallel to
the x-axis and a second ferromagnetic position sensor 1106B is
positioned on an axis that is parallel to the y-axis. Each of the
ferromagnetic position sensors 1106A and 1106B provides data for
computation of distance between it and the ferromagnetic element
1102A. Because the ferromagnetic position sensors 1106A and 1106B
are disposed at 90.degree. angles about a circumference, data from
the sensors 1106A and 1106B yields data about a position of the
flywheel rotor 1105 relative to the an axis parallel the
z-axis.
[0140] The flywheel rotor 1105 includes a levitator susceptor
1116D. The levitator susceptor 1116D may be incorporated in the
flywheel rotor 1105. The flywheel assembly 1100 also includes a
ferromagnetic sensor 1110. The ferromagnetic sensor 1110 is
positioned in the center of the enclosure 1103 and opposite the
levitator susceptor 1116D. The ferromagnetic sensor 1110 measures a
distance between itself and the levitator susceptor 1116D and
communicates data representative of the distance.
[0141] Combined data from the ferromagnetic sensors 1110 and 1106A
may be processed to determine tilt of the flywheel rotor 1105 about
the y-axis with respect to gravitational vector 1108. Combined data
from the ferromagnetic sensors 1110 and 1106B similarly yield tilt
of the flywheel rotor 1105 about the x-axis. Combined data from the
ferromagnetic sensors 1110, 1106B, and 1106A allow computation of
the flywheel rotor 1105 position on an axis parallel to the
z-axis.
[0142] The flywheel assembly 1100 includes sensors 1112A and 1112B.
The sensors 1112A and 1112B are fixed to the outer circumferential
surface of enclosure 1103. The sensors 1112A and 1112B measure
distance from each sensor to a ferromagnetic element 1104. Data
from the sensors 1112A and 1112B may be processed to determine
radial positions of the flywheel rotor 1105.
[0143] In the depicted embodiment position sensors are used with
magnetic sensors and ferrite targets. In some embodiments,
distances between the flywheel rotor 1105 and the enclosure 1103
may be measured using other types of sensors such as optical or
capacitive sensors.
[0144] FIG. 12 illustrates an example levitator assembly 1200 that
may be implemented with the flywheel assembly 1100 of FIGS.
11A-11C. FIG. 12 depicts a portion of the flywheel assembly 1100 of
FIG. 11 with the flywheel rotor 1105 and the enclosure 1103
omitted.
[0145] The levitator assembly 1200 includes a levitator pole 1116A.
The levitator pole 1116A may be fabricated from 1018 alloy steel or
a material having similar mechanical and ferromagnetic properties.
In the depicted embodiment, the levitator pole 1116A has a first
inner diameter 1202 of about 1.0 inch, a second inner diameter 1204
of about 2.50 inches, and an overall outer diameter 1206 of about
2.75 inches. The levitator pole 1116A has a first thickness 1210
(in the z-direction) of about 0.1875 inches and a second thickness
1208 of about 0.4375 inches.
[0146] Fixed to the levitator pole 1116A is a levitator magnet
1116B. The levitator magnet 1116B is a rare earth ring magnet. The
magnetic properties of the levitator magnet 1116B may be those of
rare earth magnet grade 42. In the depicted embodiment, the
levitator magnet 1116B has its magnetization direction oriented
axially as depicted by the arrow shown on the levitator magnet
1116B. The arrowhead indicating magnetic North. By reason of its
high relative magnetic permeability, the levitator pole 1116A
provides a confining path for magnetic flux provided by the
levitator magnet 1116B.
[0147] The levitator assembly 1200 includes a levitator control
coil 1116C. The levitator control coil 1116C may include about 85
turns of #26 insulated copper magnet wire helically wound in some
embodiments. The levitator control coil 1116C is positioned in the
annulus formed between the outer diameter of the levitator magnet
1116B and the opposed cylindrical surface of the levitator pole
1116A. The levitator control coil 1116C may be fixed in place using
an epoxy adhesive. The levitator control coil 1116C is connected to
and may be controllably energized by levitator control electronics
1116E. Energizing the levitator control coil 1116C may include an
electrical current of about 15 Amperes in magnitude and either
polarity being initiated by the levitator control electronics 1116E
which may flow through the levitator control coil 1116C.
[0148] The levitator susceptor 1116D is a disc made from a
ferromagnetic material. For example, the levitator susceptor 1116D
may be comprised of steel alloy 1018 or a dispersion of
ferromagnetic particles within a matrix material such as a plastic
or other substantially non-ferromagnetic material. The levitator
susceptor 1116D is subject to an attractive force generated when
positioned in proximity to a magnetic field. For example, a
controllable field presented by the levitator pole 1116A, the
levitator magnet 1116B, and levitator control coil 1116C as
controllably energized by the levitator control electronics 1116E
may subject the levitator susceptor 1116D to an attractive
force.
[0149] In the depicted embodiment, the levitator susceptor 1116D
has an outer diameter of about 3.0 inches and a thickness of about
0.25 inches. As mentioned above, the ferromagnetic sensor 1110 is a
position sensor that measures distances between itself and the
levitator susceptor 1116D. Data representative of the distances are
supplied to the levitator control electronics 1116E.
[0150] The electromagnetic field caused by passage of electric
current through levitator control coil 1116C controllably varies
magnetic flux within the levitator pole 1116A. The effect of the
magnetic flux controllably changes the attractive force exerted on
the levitator susceptor 1116D. The attractive force can be
increased or decreased depending on the magnitude and polarity of
electric current driven through the levitator control coil 1116C.
Thus, the operation of the levitator assembly 1200 positions or
re-positions the flywheel rotor 1105 relative to the enclosure
1103. Positioning or re-positioning the flywheel rotor 1105
relative to the enclosure 1103 assures no mechanical contact occurs
between the flywheel rotor 1105 and the enclosure 1103 during
operation.
[0151] On energizing the levitator assembly 1200, the levitator
control electronics 1116E with rotor axial position data from the
ferromagnetic sensor 1110 energizes the levitator control coil
1116C to set the magnitude of attractive force exerted on the
levitation susceptor 1116D. The levitator control coil 1116C lifts
flywheel rotor 1105 of FIGS. 11A-11C and its affixed components
away from physical contact with enclosure 1103. The levitator
control electronics 1116E further refine the axial levitated
position of the flywheel rotor 1105 to minimize the electrical
current sent by the levitator control coil 1116C to levitate the
flywheel rotor 1105. The current may be minimized by relying at
least partially on the permanent ring magnet 1116B, which involves
no energy supply for its force.
[0152] In some embodiments, the levitator control electronics 1116E
are programmed to position the flywheel rotor 1105 on an axis
parallel to the z-axis such that the attractive force developed by
levitator magnet 1116B as resolved on levitator susceptor 1116D is
essentially equal to the force exerted by gravity on the flywheel
rotor 1105.
[0153] Referring back to FIGS. 11A-11C, the flywheel assembly 1100
includes electromagnetic actuator elements 1114A, 1114B, 1114C, and
1114D. The actuator elements 1114A, 1114B, 1114C, and 1114D may
include coils of magnet wire that may be controllably energized to
produce forces that attract the ferromagnetic element 1104, which
is fixed to the flywheel rotor 1105. Energizing the actuator
elements 1114A, 1114B, 1114C, and 1114D cause radial translation of
flywheel rotor 1105 relative to the enclosure 1103. Magnitude and
direction of rotor translation is determined by the magnitude of
electrical current applied to one or more of the actuator elements
1114A, 1114B, 1114C, and 1114D. For example, translation in the
positive y-direction may be achieved by energizing the actuators
1114A and 1114D substantially equally, which may create two
attractive force vectors of substantially equal magnitude and
substantially equal but opposite projections along an axis parallel
to the X-axis. The two attractive force vectors resolve to a single
force vector pulling the flywheel rotor 1105 in substantially the
positive y-direction.
[0154] Referring to FIG. 11C, the flywheel assembly 1100 includes
electromagnetic actuator elements 1118A, 1118B, 1118C, and 1118D.
The electromagnetic actuator elements 1118A, 1118B, 1118C, and
1118D together controllably exert attractive force on the flywheel
rotor 1105 that can controllably tilt the flywheel rotor 1105. For
example, the electromagnetic actuator elements 1118A, 1118B, 1118C,
and 1118D cause the flywheel rotor 1105 to pivot about axes
parallel to the x-axis or y-axis through interaction with the
ferromagnetic element 1102B. Control of rotating bodies that the
computation of flywheel rotor 1105 tilt corrections, which is
referenced above, incorporate and compensate for precession effects
that are functions of rotor mass distribution and spin rate.
[0155] The electromagnetic actuator elements 1118A-1118D and
1114A-1114D may include a coil having about 50 turns of #26 magnet
wire. The average diameters of the coils may be about 0.5 inches.
The coils may be fixed opposite to their respective proximate
ferromagnetic elements at angular positions approximately
equidistant between the sensors 1106A and 1106B. The
electromagnetic actuator elements 1118A-1118D and 1114A-1114D are
controllably energized by rotor position control computation (not
depicted), which may include signal conditioning electronics,
computation, and power drive electronics. The power drive
electronics may be connected to the electromagnetic actuator
elements 1118A-1118D and 1114A-1114D.
[0156] In some embodiments, different means of actuator
construction, such as printed conductors on circuit boards, may be
employed without departing from the scope of this disclosure.
Moreover, different types of actuators, such as those which operate
through generation of Lorentz forces rather than through attraction
of ferromagnetic materials, are contemplated in this
disclosure.
[0157] With combined reference to FIGS. 11A-12, the sensors 1110,
1106A, 1106B, 1112A, 1112B, the levitator components 1116A-1116E,
the actuators 1114A-1114D, and actuators 1118A-1118D together with
computational means (not shown) effect positional control of the
flywheel rotor 1105 in 5 degrees of freedom (x-direction,
y-direction, z-direction, rotation about an axis parallel to the
X-axis, and rotation about Y an axis parallel to the y-axis).
[0158] The flywheel assembly 1100 further includes the arrays of
magnets 910A and 910B and the electromagnetic coil assemblies 912A
and 912B described with reference to FIG. 9. The arrays of magnets
910A and 910B and the electromagnetic coil assemblies 912A and 912B
effect control of the spin of the flywheel rotor 1105 about the
rotational axis 1107. In addition, the arrays of magnets 910A and
910B and the electromagnetic coil assemblies 912A and 912B operate
to store and retrieve energy from the flywheel rotor 1105 as
described elsewhere in this disclosure.
[0159] During spin operations, position control electronics
maintain the position of flywheel rotor 1105 within a defined
spatial envelope. Positioning or re-positioning the flywheel rotor
1105 occurs in response to the flywheel rotor 1105 exiting the
defined envelope or in response to a prediction that the flywheel
rotor 1105 is going to exit the defined envelop. The data
representative of the position of the flywheel rotor 1105 is used
in computations to make determinations regarding a current position
of the flywheel rotor 1105. The flywheel rotor 1105 is otherwise
not subjected to correction.
[0160] During operation, the flywheel rotor 1105 is first
positioned for spin by moving it away from contact with enclosure
1103. The arrays of magnets 910A and 910B and the electromagnetic
coil assemblies 912A and 912B are then energized to spin the
flywheel rotor 1105. In the depicted embodiment, the flywheel rotor
1105 may be accelerated to a maximum of about 110,000 RPM by
electricity produced by a PV device string (e.g., 102) at which
point the flywheel assembly 1100 holds approximately 100 Watt-hours
of kinetic energy. However, some embodiments may limit operation to
about 73% of this maximum at which the flywheel assembly may hold
about 80 Watt-hours. The stored energy may be retrieved as
described elsewhere in this disclosure to maintain electrical
output of a PV panel.
[0161] In some embodiments, the flywheel assembly 1100 may be
configured as described in U.S. patent application Ser. Nos.
13/280,232 and 13/280,314 filed Oct. 24, 2011, the disclosures of
which are incorporated herein by reference in their entireties.
[0162] Some embodiments described in this disclosure are related to
a PV panel. The PV panel is configured as a modular electrical
source with per-panel energy storage. Energy storage is added to a
PV electrical source, such as those assemblies of PV devices
commonly known as solar panels. Energy storage is provided on a
per-panel basis, i.e., energy produced by a single PV panel is
stored within a storage device located on that panel. When
electrical output of the PV panel is reduced, the storage device
delivers energy stored thereon to the panel's electrical load. Such
per-panel energy storage continues a panel's nominal electrical
output if insolation of the PV panel is interrupted or diminished,
thereby eliminating or reducing rapid output variations and
electrical distribution grid instabilities associated with solar
photovoltaic electrical sources.
* * * * *